doc: add doc on joining testnet using snapshot

README.md

@@ -108,6 +108,25 @@ rm -rf ~/.sedad || true
 ./sedad start
 ```
 
+### Joining testnet using snapshot
+
+We recommend joining the testnet using a snapshot that has been taken after the most recent upgrade.
+The SEDA team is planning to provide links for downloading snapshots soon, but for now you may use the snapshot provided by Lavender.Five Nodes.
+
+```bash
+$BIN join <moniker> --network testnet
+
+# Backup private validator state file if you'd like.
+cp $HOME/.sedad/data/priv_validator_state.json $HOME/.sedad/priv_validator_state.json.backup
+
+# Download snapshot, decompress it, and place it under chain directory.
+wget https://snapshots.lavenderfive.com/testnet-snapshots/seda/seda_450477.tar.lz4
+lz4 -dc < seda_450477.tar.lz4 | tar xvf - -C $HOME/.sedad
+
+$BIN start
+```bash
+Lavender.Five Nodes also provides detailed instructions [here](https://snapshots.lavenderfive.com/testnet-snapshots/seda/seda_450477.tar.lz4).
+
 ### Running the Node Yourself Dockerized
 
 For instructions how to run the node yourself as a normal node or a validator in [docker](https://www.docker.com/).